North Korean leader Kim Jong-un is visiting the Chinese city of Dalian to meet his Chinese counterpart Xi Jinping, according to reports.

If the reports are true, Kim seems to be involved in last-minute diplomatic coordination with Xi before his historic summit with U.S. President Donald Trump. Trump has said the date and place for the summit with Kim are set, saying "stay tuned."

The Chinese foreign ministry remained silent over the rumors. South Korea's foreign ministry hinted at Kim visiting China, but did not specify.

A foreign ministry official told reporters on Tuesday afternoon that the ministry "keeps an eye on what's happening." The official said he has "nothing to share, with nothing officially announced yet in Beijing."

South Korea's Yonhap News Agency first reported on "a high-ranking North Korean official visiting Dalian" on Monday. Citing multiple anonymous sources, the news wire said the official flew in a private plane and arrived at Dalian airport on Monday amid heavy security.

Yonhap did not identify the official. But rumors are spreading on Chinese social media that it is Kim.

Seoul-based broadcaster KBS reported that Dalian airport was closed to the public from 8 a.m. to 1 p.m. on Monday and roads around the Bangchuidao Guesthouse in the city were also closed Monday afternoon. The guesthouse is normally reserved for foreign VIP visitors.

There is speculation that the North Korean official is visiting to attend the launch of China's first domestically built aircraft carrier, the Type 001A.